1. Field of the Invention
This invention relates to automated data storage libraries and more particularly relates to an automated data storage library configured to perform an abbreviated calibration of one or more accessors. The abbreviated calibration allows the library to be made available to hosts more quickly than conventional calibration techniques.
2. Description of the Related Art
Automated data storage libraries are known for providing cost effective storage and retrieval of large quantities of data. The data in automated data storage libraries is stored on data storage media that are, in turn, stored on storage shelves or the like inside the library in a fashion that renders the media, and its resident data, accessible for physical retrieval. Such media is commonly termed “removable media.” Data storage media may comprise any type of media on which data may be stored and which may serve as removable media, including but not limited to magnetic media (such as magnetic tape or disks), optical media (such as optical tape or disks), electronic media (such as PROM, EEPROM, flash PROM, COMPACTFLASH™ cards, SMARTMEDIA™ cards, MEMORY STICK™ cards, etc.), or other suitable media. Typically, the data stored in automated data storage libraries is resident on data storage media that is contained within a cartridge and referred to as a data storage media cartridge. An example of a data storage media cartridge that is widely employed in automated data storage libraries for mass data storage is a magnetic tape cartridge.
In addition to data storage media, automated data storage libraries typically contain data storage drives that store data to, and/or retrieve data from, the data storage media. The transport of data storage media between data storage shelves and data storage drives is typically accomplished by one or more robot accessors or pickers (hereinafter termed “accessors”). Such accessors have grippers for physically retrieving the selected data storage media from the storage shelves within the automated data storage library and transport such media to the data storage drives by moving in the X and/or Y directions. Depending on the library design, more complicated movement may include a Z direction and even radial movements of the gripper.
In order to accommodate certain mechanical tolerances within the hardware of an automated data storage library, the automated data storage library performs a calibration to account for differences between where hardware is expected to be and where it is actually located. Performing such a calibration allows greater tolerances in the design and manufacture of the library components, which results in a more affordable end product. Calibration techniques also may be applied in error recovery procedures to compensate for hardware or software problems that may develop over time.
However, calibrating an accessor within an automated data storage library may necessitate that the library be and remain off line for a significant duration of time. Depending on the size and contents of an automated data storage library, the calibration process may take several minutes or more for each storage frame within the library. It is apparent that calibrating an accessor to every shelf, slot, drive, and so forth, can dramatically affect the availability and performance of an automated data storage library. Additionally, some automated data storage libraries incorporate multiple accessors. For every accessor that must be calibrated to the entire library, conventional calibration techniques require 100% more time than for calibration of a single accessor. For example, calibrating two accessors may take twice as much time as calibrating a single accessor.
Some calibration techniques have been implemented to decrease the amount of time needed to calibrate an automated data storage library. Some libraries, for instance, calibrate multiple columns of storage shelves by calibrating only the outside columns and using interpolation to predict the location of intermediate columns and shelves. Regardless of these conventional techniques, however, the time required to calibrate one or more accessors to an entire automated data storage library is substantial and should be further reduced.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that performs an abbreviated calibration of a data storage library. Beneficially, such an apparatus, system, and method would calibrate one or more accessors within an automated data storage library in less time than conventional library calibration methods and systems.